1. Field of the Invention
The present invention relates to a membrane-electrode assembly for a fuel cell and a fuel cell including the membrane-electrode assembly. More particularly, the present invention relates to a membrane-electrode assembly that has strong adherence between an electrode substrate and a catalyst layer and that permits smooth mass transfer, and a fuel cell including that membrane-electrode assembly.
2. Description of the Related Art
A fuel cell is a power generation device producing electrical energy through an electrochemical redox reaction between an oxidant and a fuel such as hydrogen, or a hydrocarbon-based material such as methanol, ethanol and natural gas.
Representative exemplary fuel cells include a polymer electrolyte membrane fuel cell (PEMFC) and a direct oxidation fuel cell (DOFC). Direct oxidation fuel cells include direct methanol fuel cells which use methanol as a fuel.
Polymer electrolyte fuel cells have the advantages of high energy density and high power, but also have the problems of requiring careful handling of the hydrogen gas and requiring accessory facilities such as a fuel reforming processor for reforming methane or methanol, natural gas, and the like in order to produce hydrogen as the fuel gas.
On the contrary, although the energy density of the direct oxidation fuel cell is lower than that of the gas-type fuel cell, it has the advantages of easy handling of the liquid-type fuel, low operation temperature, and no need for additional fuel reforming processors. Therefore, the direct oxidation fuel cell has been acknowledged as an appropriate system for a portable power source for use as small and common electrical equipments.
In the above-mentioned fuel cell, a fuel cell stack that generates substantial electricity includes several to scores of unit cells stacked adjacent to one another, and each unit cell is formed with a membrane-electrode assembly (MEA) and a separator (which is also referred to as a bipolar plate).
The membrane-electrode assembly is composed of an anode (which is also referred to as a “fuel electrode” or an “oxidation electrode”) and a cathode (which is also referred to as an “air electrode” or a “reduction electrode”), that are separated by a polymer electrolyte membrane.
The anode and the cathode are generally composed of an electrode substrate, such as a carbon paper or a carbon cloth, and a catalyst layer. An electrode having this structure has a weak adherence between the electrode substrate and the catalyst layer, thereby deteriorating fuel diffusion.
The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore, it should be understood that the above information may contain information that does not necessarily form the prior art or the described art that is already known in this country by a person or ordinary skill in the art.